Divers have discovered what is thought to be the world's oldest drinkable champagne in a shipwreck in the Baltic Sea, one of the finders said Saturday. They tasted the one bottle they've brought up so far before they even got back to shore.

Diving instructor Christian Ekstrom said the bottles are believed to be from the 1780s and likely were part of a cargo destined for Russia. The nationality of the sunken ship has not yet been determined.

"We brought up the bottle to be able to establish how old the wreck was," he told The Associated Press. "We didn't know it would be champagne. We thought it was wine or something."

Ekstrom said the divers were overjoyed when they popped the cork on their boat after hauling the bubbly from a depth of 200 feet (60 meters).

"It tasted fantastic. It was a very sweet champagne, with a tobacco taste and oak," Ekstrom said.

The divers discovered the shipwreck Tuesday near the Aland Islands, between Sweden and Finland. About 30 bottles are believed to be aboard the sunken vessel.

Ekstrom said he is confident of the champagne's age and authenticity, but samples have been sent to laboratories in France for testing. "We're 98 percent sure already because of the bottle (we found)," he said.

Swedish wine expert Carl-Jan Granqvist said each bottle could fetch euro50,000 ($68,000) if the corks are intact and the sparkling drink is genuine and drinkable.

"If this is true, it is totally unique," said Granqvist, one of the experts contacted by Ekstrom and his team. "I don't know of any other (drinkable) bottle this old. I've never even heard of it."

Granqvist said he had seen pictures of the bottle, and it had languished in near-perfect storage conditions - in the dark at a constant cold temperature.

"If it's the right atmosphere outside, and inside the bottle the cork is kept dry in the middle; it keeps itself," he said.

According to French champagne house Perrier-Jouet, a subsidiary of Pernod Ricard, their vintage from 1825 is the oldest recorded champagne still in existence.